Hey!
Congratulations on getting the interview, what a fantastic achievement!
Most first-stage interviews will be relatively conversational, with the aim of learning more about your motivations and skillset. You can expect questions around your motivation for law, why
Gibson Dunn specifically, and competency-based questions (such as showing examples of teamwork, resilience, or attention to detail).
It really helps to have a strong answer for why
Gibson Dunn in particular. I would make sure to refresh your research of the firm and have a look at a few of their standout deals (especially in their main practice areas), as well as think about what attracts you to their US firm culture in London. Try to show you understand how they differ from other US firms in London, such as their focus close trainee supervision and smaller intakes.
Also, have a few thoughtful questions ready for the interviewer - these do not have to be overly technical, but you should show some genuine curiosity in learning more about the firm and the application process. I would usually prepare 2-3 in advance, but it's also good to bring up questions that pop up on the day!
Overall, whilst you should show clear motivations and knowledge of the firm, it is a chance to get to know you better - stay relaxed, be yourself, and show enthusiasm for the firm and its work. Best of luck!